Fear of falling

Nov 22, 2011

Konstantin Bogdanov

Phobos-Grunt will fall to Earth in January 2012, according to Vladimir Popovkin, head of the Russian Space Agency, Roskosmos, but no one can determine where the satellite will fall or what the damage might be.

The Phobos-Grunt space probe seems to be doing fine, floating in space,
maintaining its orientation towards the sun. But here on earth, it has lived up
to its name – Phobos is Greek for “fear” – due to its failure to leave the
earth’s orbit.

“All the systems on the spacecraft are working normally and it is
orientated towards the sun. So far, we are trying to find out what needs to be
done to rectify the situation,” said Vladimir Popovkin, the general director of
the Russian space agency.

But inevitably, after a while, the orbit will sag and the spacecraft
will be left with two possible scenarios: orbit correction or reentry and
subsequent fall.

At the moment, the possibility that the probe will be able to find its
proper orbit is unlikely since there is no communication with it. And so, the
second scenario is almost inevitable.

Popovkin has said the probe “will be flying through January,” and
independent Canadian expert Ted Molczan concurs. More precise forecasts of the
time of the fall are not available and, given such an error margin, where the
spacecraft will fall cannot be predicted.

“Every hour brings more data, so, by the projected time of the fall, we
will know the area with a fair degree of accuracy,” a Russian ballistics expert
said on condition of anonymity.

So far, the set of projections of the spacecraft’s trajectory to the
Earth’s surface has resulted in the identification of an 11,000 km strip of land
parallel to the equator. The short life of the stricken station will end
somewhere within that corridor. However, as Igor Lisov, editor of the Russian
journal “Novosti Kosmonavtiki” (Space
News), pointed out: “That covers half of North and South America, Australia,
the whole of Africa and half of Eurasia.”

It is also hard to predict how the fully fueled main propulsion unit
will behave when the craft falls out of orbit.

The main fears are connected with the fuel, heptyl. In addition to being
a strong poison, rocket fuel can cause genetic mutations. But all the present
signs are that the bulk of the hazardous liquid will burn up together with the
main metal structures or will scatter in the upper layers of the atmosphere
upon reentry.

“There are 7.5 tons of fuel; it is in aluminium tanks and we have no
doubt that it will blow up upon reentry into the dense layers of the
atmosphere. It is unlikely that any at all will reach the Earth,” Popovkin said
last week.

The stuff that they dropped

Near Earth spaceflights have a dismal experience of losing probes with
far more dangerous content than heptyl in Phobos. Some highly radioactive
materials have been lost.

Source: Russia Today

In the 1970s, the Soviet Union started making intensive use of low-orbit
satellites for radar reconnaissance, which required considerable power to feed
the radars. Small nuclear reactors were installed on board for this purpose.

Such probes were the basis of the orbital component of the marine space
intelligence and targeting satellite Legenda, which enabled Russian submarines
to count on hitting the U.S. aircraft carrier fleet with heavy anti-vessel
missiles from a distance of 400-700
km.

After it spent its resources, the craft was not dropped back into the
atmosphere complete: the reactor module was detached and parked in “burial
orbits” in space, where they bob to this day.

However, occasionally satellites hurtle into the atmosphere together
with the reactor and its contents. The most famous fall took place in January
1978, when a Kosmos-954 satellite disintegrated over northern Canada,
sprinkling radioactive debris over a fairly long strip of sparsely populated
territory to the northeast of Great Slave Lake.

After a prolonged fight, the Soviet government paid the Canadians
several million dollars in compensation for environmental damage.

In another case, the Americans jettisoned a radioisotope source of
plutonium along with a lunar module before the crash landing of Apollo 13. They
did not bother to search for it, letting it sink somewhere in the Pacific.
There have also been numerous cases of emergency scuttling of satellites with
potentially “dirty” contents. Mars-96, which met with an accident before
Phobos, had plutonium isotope generators.

Strictly speaking, therefore, the people of earth have dropped all sorts
of manmade objects on their heads. Against this background, the fall of
Phobos-Grunt is an unpleasant but not a catastrophic event.